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Computer Sound October 23 (Day); October 10 (Night) There are four components for capturing and outputting sound on a computer (p. 341): o Sound card o Speakers o Microphone o Recording / playback software
Sound Card:
o A sound card is an expansion card that provides sound input to and sound output
from a computer. o Sound passes through three stages when it is computerized:
Digitize or input the sound. Digitizing is simply the processing or
converting of the analog sound waves into binary 1s and 0s. Store digital data in compressed data file.
Reproduce or synthesize the sound. Synthesize means to convert the
digital 1s and 0s into analog sound waves that can be played through the speakers. o Jacks: Virtually every sound card comes with at least three connections (p. 347):
The line out jack is used to connect an external device such as a
cassette or CD player and output sounds from your computer through that device.
The line in jack is used to connect an external device such as a
cassette or CD player and input sounds from that device.
The rear out jack connects to speakers.
Most sound cards also have a microphone jack for voice input.
Sound Card Jacks o Most sound cards have a game controller port for connecting joysticks, gamepads, etc. o Speakers:
Stereo is the oldest speaker technology that you will see in the computer
world. It consists of two speakers – a left and a right – that share a common jack (p. 349).
A 2.1 speaker consists of a pair of standard stereo speakers and a
subwoofer connected to a shared jack (p. 349).
A subwoofer adds an extra dimension to your sound by adding
low-frequency tones (p. 345).
A 5.1 speaker supports five channels of sound – front-left, front-right,
front-center, rear-left, and rear-right (p. 349). Sound Capture:
o Sound waves are captured (recorded) in an electronic format through a process called
sampling. Sampling is the process of taking samples of the sound at certain intervals. The more samples you take, the better your sound will be. The more samples you take, however, the more space it will require (p. 341).
The sampling rate is measured in units of thousands of cycles per
second, or kilohertz, KHz (p. 341). Sounds have three primary characteristics that have to be digitized: Loudness Tone
Sound Formats: o A four-minute WAV formatted song can take up to 40+ megabytes to store (p. 342) meaning that it typically takes 650 MB to store an entire CD of music. o The human ear cannot hear nearly all of the small variations of sound recorded at 44 KHz and 16-bit depth. Therefore, programmers have created programs to throw out the unnecessary characteristics of a file (p. 342).
o These programs are called compressor/decompressor programs called codecs (p.
o Popular formats include MP3, ASX, and RM (pp. 342-344). MIDI:
o Another sound format is the Musical Instrument Digital Interface (MIDI) file (p.
o MIDI files aren’t actually music files. Instead, they are text files that contain
instructions that tell the sound card what notes to play, how long, how loud, which instruments, etc (p. 343). o MIDI files are small, but lack quality (p. 343).
